6 to 8 hours for an average size house and deck
Ready to start painting the outside of your house? Cool! First you need to pressure wash the house. Even if it doesn’t look dirty, there’s grime there that you can’t see. Pressure washing will create a clean surface for the new paint to adhere to and it is a critical first step if you want to paint your house right!
First, you’ll need to get your hands on a pressure washer because a regular garden hose is too weak to do the job right. Consider spending $250-$300 to get a 2500+ PSI gas-powered pressure washer, the kind with wheels and a long handle and a holster to hold the spray gun. A pressure washer is a handy thing to have around the house for a variety of reasons. Don’t buy one of those chintzy electric pressure washers no matter how much PSI it claims to have. On the other hand, you could spend $400-plus on a more powerful pressure washer if you expect to use it a lot in the future, although the $250 ones work just fine in my opinion. You’ll also need a good quality 50-foot garden hose.
The best thing about washing a house is that it doesn’t require much elbow grease because the wonderful world of chemistry lends a hand. There are a variety of house detergents on the market; I like JO-MAX (made by Zinsser) because I’ve found it to be especially potent when attacking mold, mildew, and grime. Mix 4 gallons of water, 3 quarts of bleach, and 1 quart of JO-MAX in a 5-gallon bucket (you might want to split it between two buckets).
Pour some of the mixture into a pump-up garden sprayer and pressurize it. Then pick out a section of the house and soak the area thoroughly, splashing every nook and cranny with the chemical solution, starting near the ground and working your way up so the solution keeps running back down on itself. Pressurize the pump as needed to keep a good stream flowing. Don’t skimp with the chemicals because if the mold and grime aren’t killed and broken down, the pressure washer itself won’t do much good. And avoid tackling too big of a section at once, because you don’t want the chemical solution to dry before you have a chance to wash it off.
If you’re concerned the chemicals will harm your flowers and foliage—a real possibility—soak them with a garden hose immediately before washing a nearby section, then rinse them clean immediately afterward. This might require unhooking and re-hooking the hose from the pressure washer from the hose, which is a hassle, but it does save the plants. If the foliage consists of burly bushes as opposed to frail flowers, you can stand 20 feet back and do the pre-soak and post-rinse with the pressure washer. It’s not ideally suited to that task, however.
After spraying the solution onto a section, allow the chemicals a few minutes to kill the mold and mildew spores and eat away the grime on the siding, then start pressure washing the streaky mess off, again making sure to hit every inch of the painted surface. This time, though, start at the top and work your way down, rinsing thoroughly as you go. As far as water force goes, remember that the chemicals are doing the real work, so don’t hold the nozzle of the pressure washer too close to the house or it could do damage, especially to wood siding. Keep the fan-width of your spray about eight- to twelve-inches wide on the siding and you are probably applying the proper amount of water pressure.
If the house is peeling badly, expect a lot of chips to come flying off, but don’t be tempted to use the pressure washer in place of scraping–you don’t want to hold the nozzle that close to the siding because you’ll damage it. Sometimes water leaks into the house through the window frames, so it helps to have somebody positioned inside ready to wipe it up. Wear rain gear for the power washing festivities, but don’t expect to stay dry; the suit is mostly to block the chemicals. Wear safety glasses if you can’t stand the burning bleach in your eyes (and to protect from flying paint chips), but bring a clean rag along to keep wiping the lenses clear so you can see what you’re doing. Rubber boots are also nice, but whatever boots you wear, be careful climbing up and down wet ladders with wet boots. It’s easy to slip, so pay attention.
Washing the house isn’t a lot of fun, but it’s a critical first step so it must be done well. Afterward give the house (and yourself) two or three days to dry out. And please don’t joke that the house looks so good now it doesn’t even need to be painted. That one has been beat to death.